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X-rays and ECGs (Electron Beams (thermionic emmission (to produce X-rays…
X-rays and ECGs
Electron Beams
thermionic emmission
to produce X-rays need...
cathode
a filament acts a cathode (-ve charge electrode)- filament heated- gives energy to electrons- they "boil off- process called THERMIONIC EMSSION
anode
electrons that boil of cathode accelerate towards anode by a potential difference between cathode and anode- when electrons collide with anode some of KE is converted into xrays
evacuated gas tube
creates a vacuum- prevents electrons colliding with air particles- knocked off target
kinetic energy (J) = charge (C) x pd (voltage- V)
current (A) = number of particles (per second) x charge (C)
X-ray intensity and absorption
x-rays are ionising because...
very high frequency
high energy
can be dangerous- ionise body cells- removing electrons from atoms, leaving them as positively charged ion
can lead to tissue damage or cancer
intensity of radiation
depends on distance from source
twice as far from the source- radiation spread 4 times the area- INVERSE SQUARE RELATIONSHIP
thickness of materials effects X-ray absorption
more dense / thicker, the more radiation absorbed
lead & concrete are used to reduce peoples exposure to X-rays in hospitals